1. Technical Field
The present disclosure relates to a backlight unit, and more particularly, to a backlight unit using a microwave plasma ultraviolet lamp as a light source and a liquid crystal display including the same.
2. Discussion of the Related Art
A liquid crystal display (LCD) is a device in which a desired image is displayed on a liquid crystal display panel by adjusting the transmissivity of light passing through the panel. A transmissive or transflective LCD, except a reflective LCD using external incident light such as natural light, may employ a backlight unit as a light source to display an image. A fluorescent lamp has been used as the light source of the backlight unit.
The backlight unit has been classified into an edge type and a direct type according to the position of the light source. In the direct type backlight unit, a plurality of light sources are placed below an LCD panel to directly irradiate a front surface of the LCD panel. On the other hand, in the edge type backlight unit, a light guide plate is installed below an LCD panel and a light source is installed to a side of the light guide plate such that light incident on the side of the light guide plate can be vertically outputted and irradiated to the LCD panel.
A fluorescent lamp such as a cold cathode fluorescent lamp (CCFL) has been used as a light source. A fluorescent lamp may comprise a lamp tube including a tube body made of glass, a phosphor layer formed on an inner surface of the tube body and a discharge gas such as mercury filled in the tube body. The fluorescent lamp may also include an electrode unit including lamp electrodes disposed respectively at inner and outer sides of the tube body and a lead. In the fluorescent lamp so configured, when electric power is applied to the lamp electrodes from the outside through the lead, electrons existing in the lamp tube collide against the electrodes to thereby generate secondary electrons. The secondary electrons collide against the discharge gas in the tube body to thereby generate ultraviolet light. Such ultraviolet light is converted into visible light while passing through the phosphor layer.
A large amount of heat is generated from the fluorescent lamp during this process. Further, lowering of brightness, and non-uniform emission of light, for example, occur over time due to, for example, phosphor layer degradation, and electrode contamination. Since the expected life of the liquid crystal display is dependent on the expected life of the fluorescent lamp, the above factors lower the expected life and reliability of the liquid crystal display. Further, the heat generated from the fluorescent lamp causes deformation of the fluorescent lamp and several optical sheets disposed adjacent to the fluorescent lamp, and thus, the entire backlight unit may malfunction. Furthermore, the number of the fluorescent lamps and inverters corresponding to the number of fluorescent lamps causes increased manufacturing costs of the backlight unit and spatial limitations on the backlight unit upon the installation thereof.